Multiple-time programming apparatus and method using one-time programming element

ABSTRACT

A multiple-time programming apparatus and method using one-time programming (OTP) elements are provided. The apparatus comprises a first adjusting OTP element, a second adjusting OTP element and a logic device. An adjusting data is written into the first adjusting OTP element. When a modification in an IC is desired, the value of a desired data and the prior adjusting data is performed exclusive-OR (XOR, hereinafter) together and written into the second adjusting OTP element. The logic device performs XOR on the first OTP signal outputted from the first adjusting OTP element and the second OTP signal outputted from second adjusting OTP element, and outputs the resulting OTP signal with desired value. Thus, the apparatus and the method according to an embodiment of the present invention allow modification of data using the OTP elements that prevents from using expensive multiple-time programming elements.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the priority benefit of Taiwan applicationserial no. 93115036, filed on May 27, 2004. All disclosure of the Taiwanapplication is incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an integrated circuit (IC,hereinafter). More particularly, the present invention relates to amultiple-time programming apparatus and a method using one-timeprogramming elements.

2. Description of Related Art

In a proceeding of an integrated circuit manufacture, the electricalparameters of each integrated circuit may vary from lot to lot, and varyfrom wafer to wafer of the same lot, and even vary from die to die ofthe same wafer. There are different process variations such as deviationof ion implantation, deviation of gate oxide thickness, and error inetching. Such variation of process will cause frequency deviation of anoscillator, or voltage deviation of a regulator. If the electricalparameters of an integrated circuit vary beyond the specification, e.g.over 5% deviation of the IC specification, the IC is identified asdefective during testing process. Therefore, the IC manufacturersusually perform some post-fabrication fine-tuning of the parametersmentioned above in order to increase IC production yield. Since theaforementioned parameters always change along with the variation ofprocess parameters, one-time programming (OTP, hereinafter) elements,e.g. fuse or metal wire, are used usually for fine-tuning to keepconsistency of an output lot. Generally speaking, the methods offine-tuning an IC at ex-factory effectively increase the productionyield.

Common OTP adjusting methods for integrated circuit includes laser trimand poly fuse, also known as E-fuse. The OTP element used in laser trimis a metal wire, and it is programmed by blowing the metal wire withhigh energy laser. The OTP element used in poly fuse is a poly wire(a.k.a. poly fuse), and it is programmed by blowing the poly wire with alarge current or by changing the resistance of the poly wire through theelectron migration caused by a large current. To find out whether an OTPelement is programmed, the metal wire or ploy wire is detected for opencircuit or change of resistance by reading the circuit. Theaforementioned programming process is irreversible, i.e. the elementcannot be reprogrammed once it is programmed.

In using an OTP element, e.g. a poly fuse, the element cannot beprogrammed again once it is programmed (blowed), hence the parameter cannot be re-adjusted, i.e. it is not multiple-time programmable. However,from the users prospective, it is desired that the parameters can bere-programmed or modified several times even after they are programmedby IC manufacturer at ex-factory. Take STN LCD driver ICs for example,although the operating voltage VLCD of STN LCD driving waveform isadjusted to an accurate value at ex-factory of the IC. However in theSTN LCD module factory, the variation in characteristics of liquidcrystal formula and deviation of cell gap may cause the contrast ratiodeviation of the STN LCD module, which makes it a defective product. Insuch case, it is desired for the STN LCD module factory that theoperating voltage VLCD of STN driver can be fine-tuned again to increasethe production yield of STN LCD module.

Therefore, in the prior art, Multiple-Time Programming (MTP,hereinafter) elements, e.g. Erasable Programmable Read-Only-Memory(EPROM, hereinafter), Electrically Erasable ProgrammableRead-Only-Memory (EEPROM, hereinafter), and FLASH memory are adopted toperform multiple-time programming. However, MTP elements are unfavorablebecause of more expensive process, for example, a common STN LCD driverIC is manufactured with a 0.35 μm 3.3V/18V high voltage process. Addinga MTP element such as an EEPROM into the IC requires several additionalmasks, thereby increasing the manufacturing cost. The additional masksalso reflect to longer manufacturing time and delivery lead-time, andlower production yield. Furthermore, fewer foundries are equipped withtechnologies for implementing the process fabricating MTP elements.Adopting MTP elements makes it difficult to find more appropriatesubcontract foundries, hence endanger the productivity dispersion.

SUMMARY OF THE INVENTION

Accordingly, the present invention is directed to a multiple-timeprogramming apparatus using OTP elements. Logic devices are utilized toperform exclusive-OR (XOR, hereinafter) on the OTP signals outputtedfrom a plurality of adjusting OTP elements, the apparatus allows desiredadjustment of parameters that can be written separately to outputdifferent signals. Thus, the disadvantages of prior art, whereprogramming process is irreversible or the OTP element cannot bereprogrammed once it is programmed, can be effectively resolved.

The present invention is also directed to a multiple-time programmingmethod using OTP elements. According to an embodiment of the presentinvention, the OTP signals outputted from a plurality of adjusting OTPelements are performed XOR together to output a signal with a desiredspecification or characteristics. Accordingly, the method according toan embodiment of the invention allows desired adjustment of parametersthat can be written separately to output different signals. Thus, thedisadvantages of prior art where programming process is irreversible orthe OTP element cannot be reprogrammed once it is programmed can beeffectively resolved.

According to an embodiment of the present invention, the apparatuscomprises a first adjusting OTP element for outputting a first OTPsignal, a second adjusting OTP element for outputting a second OTPsignal and a logic device. Wherein the logic device is coupled to thefirst adjusting OTP element and the second adjusting OTP element. Thelogic device performs XOR on the values of the first OTP signal and thesecond OTP signal and output a signal with a value equivalent to the XORvalues of the first OTP signal and the second OTP signal.

According to another embodiment of the present invention, the apparatuscomprises N+1 groups of adjusting OTP elements and N logic devices. Forexample, the N+1 groups of adjusting OTP elements comprises a firstgroup, a second group . . . and N+1^(th) group of adjusting OTPelements, and the N logic devices may comprise a first, a second . . .and the N^(th) logic device, where N is an integer greater than 1. Everyadjusting OTP element is capable of outputting an OTP signal and everylogic device is capable of outputting an adjusting signal. The Nth logicdevice is coupled to the N+1^(th) group of adjusting OTP elements andthe N−1^(th) logic device, whereby the value of the OTP signal from theN+1^(th) group of adjusting OTP elements and the value of the adjustingsignal from the N−1^(th) logic device can be performed XOR together tooutput signals with values equivalent to the XOR values of the OTPsignal from the N+1^(th) group of adjusting OTP elements and theadjusting signal from the N−1^(th) logic device. The first logic deviceis coupled to the first group of adjusting OTP elements and the secondgroup of adjusting OTP elements, whereby the values of OTP signals fromthe first group adjusting of OTP elements and the second group ofadjusting OTP elements can be performed XOR together to output signalswith values equivalent to the XOR values of OTP signals from the firstgroup adjusting of OTP elements and the second group of adjusting OTPelements.

According to an embodiment of the present invention, the apparatusfurther comprises writing devices coupled to the adjusting OTP elementssuch that the adjusting data can be written into each adjusting OTPelement separately.

According to another embodiment of the present invention, amultiple-time programming method using OTP elements is provided. First,N+1 groups of adjusting OTP elements, for example, a first group, asecond, . . . and a N+1^(th) group of adjusting OTP elements, areprovided, wherein N is an integer greater than 1. Each adjusting OTPelement is capable of outputting an OTP signal. Next, values of OTPsignals from the first group of adjusting OTP elements and the secondgroup of adjusting OTP elements are performed XOR to output a firstadjusting signal. Likewise, the values of signals from different groupsof OTP elements among the N+1^(th) group of adjusting OTP element andthe N−1^(th) adjusting signal are performed XOR respectively to outputan N^(th) adjusting signal.

According to an embodiment of the present invention, aforementionedmethod further comprises writing a plurality of adjusting data intoadjusting OTP elements to output a desired OTP signal. Since the N^(th)adjusting signal is an XOR result of all the OTP signals from the firstthru the N+1^(th) group of adjusting OTP elements, therefore it ispossible to modify the value of the N^(th) adjusting signal multiplenumber of times by writing adjusting data into every adjusting OTPelement accordingly. Accordingly, multiple-time programming can beachieved.

According to an embodiment of the present invention, the OTP element canbe a metal wire or a poly fuse, wherein the metal wire can be adjustedwith a laser and the poly fuse can be adjusted with an electric current.Furthermore, the OTP element can be an element programmable for at leastone time as well, e.g. EPROM, EEPROM or Flash Memory. However, the scopeof the present invention is not limited to the aforementioned devices.

The multiple-time programming apparatus and method using OTP elementaccording to an embodiment of the present invention can achievefunctions similar to that of expensive MTP elements, and therefore thecost can be effectively reduced. In other words, the apparatuscomprising OTP elements according to the present embodiment of thepresent invention serves as an MTP element. Meanwhile, the process offabricating the apparatus according to the present embodiment of thepresent invention do not require special process and is applicable tomost foundries and their manufacturing processes, and the overallproduction cost can be effectively reduced.

In order to the make the aforementioned and other objects, features andadvantages of the present invention comprehensible, an embodimentaccompanied with figures is described in detail below.

It is to be understood that both the foregoing general description andthe following detailed description are exemplary, and are intended toprovide further explanation of the invention as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings are included to provide a furtherunderstanding of the invention, and are incorporated in and constitute apart of this specification. The drawings illustrate embodiments of theinvention and, together with the description, serve to explain theprinciples of the invention.

FIG. 1 is a schematic block diagram for an apparatus for two-timeprogramming using OTP elements according to an embodiment of the presentinvention.

FIG. 2 is a schematic block diagram for an apparatus for multiple-timeprogramming using OTP elements according to an embodiment of the presentinvention.

DESCRIPTION OF THE EMBODIMENTS

Referring to FIG. 1, a schematic block diagram for an apparatus fortwo-time programming using OTP elements according to an embodiment ofthe present invention is shown.

As shown in FIG. 1, the apparatus includes a logic device 110 coupled toa first adjusting OTP element 100 and a second adjusting OTP element102. The apparatus further includes a writing device 120 coupled to thefirst adjusting OTP element 100 and the second adjusting OTP element102.

According to an embodiment of the present invention, the first OTPsignal and the second OTP signal are performed XOR together by the logicdevice 110 so that an adjusting signal with a value equivalent to theXOR values of the first OTP signal and the second OTP signal can beoutput. Wherein the first OTP signal is outputted from the firstadjusting OTP element 100 and the second OTP signal is outputted fromthe second adjusting OTP element 102. Since no adjusting data waswritten into the first adjusting OTP element 100 or the second adjustingOTP element 102, the initial values are 0 for both the first and thesecond OTP signals. Hence the value of the adjusting signal outputtedfrom the logic device 110 is also 0.

When modifying the IC for the first time, the writing device 120 writesa first adjusting data into the first adjusting OTP element 100 only.The logic device 110 performs XOR on the values of the first and secondOTP signals to output an adjusting signal with the first adjusting databecause and the value of the second OTP signal is 0 since no adjustingdata was written therein.

Thereafter, when it is required to further modify the IC output signalor desired to rewrite a new adjusting data, the values of the desiredsignal and the first adjusting signal are performed XOR together forobtaining the second adjusting data. This second adjusting data is thenwritten into the second adjusting OTP element 102 by the writing device120. Next, the logic device performs XOR on the values of the first OTPsignal and the second OTP signal to output a desired second adjustingsignal.

For example, the value of the first adjusting signal is 0001 and thevalue of desired second adjusting signal is 0010. Thus, the value ofsecond adjusting data is 0001⊕0010=0011 and the value outputted from thelogic device is 0001⊕0011=0010, which is the desired second adjustingsignal.

Similarly, according to the aforementioned embodiment, when it isdesired to write adjusting data for N number of times (N is an integergreater than 1), i.e. multiple-time programming, N+1 groups of adjustingOTP elements are used.

Referring to FIG. 2, N+1 groups of adjusting OTP elements 200˜208 and Nlogic devices 210˜216 are provided. The N+1 groups of adjusting OTPelements 200˜208 may comprise a first group of adjusting OTP element200, a second group of adjusting OTP element 202 . . . and a N+1^(th)group of adjusting OTP element 208; and the N logic devices may comprisea first logic device 210, a second logic device 211 . . . and a Nthlogic device 216.

Wherein, the first logic device 210 is coupled to the first group ofadjusting OTP element 200 and the second group of adjusting OTP element202; the N^(th) logic device 216 is coupled to the N+1^(th) group ofadjusting OTP element 208 and the N−1^(th) logic device 214. The firstlogic device 210 performs XOR on the values of the OTP signals from thefirst group of adjusting OTP element 200 and the second group ofadjusting OTP element 202 to output an adjusting signal with a valueequivalent to the XOR values of signals from first group of adjustingOTP element 200 and the second group of adjusting OTP element 202. TheN^(th) logic device 216 performs XOR on the values of the OTP signalfrom the N+1^(th) group of adjusting OTP element 208 and the adjustingsignal from the N−1^(th) logic device 214 to output an adjusting signalwith a value equivalent to the XOR values of the OTP signal from theN+1^(th) group of adjusting OTP element 208 and the adjusting signalfrom the N−1^(th) logic device 214.

It is understood from above descriptions, the final output signal=thefirst OTP signal⊕the second OTP signal⊕ . . . ⊕the N+1^(th) OTP signal.

Accordingly, in the present embodiment, when the IC is modified for thefirst time, the writing device 220 writes the first adjusting data intothe first adjusting OTP element 200 only to output the first OTP signalwith first adjusting data. According to aforementioned circuit designrule of the present invention, the final output signal=the first OTPsignal⊕the second OTP signal⊕ . . . ⊕the N+1^(th) OTP signal, whereinthe second OTP signal=the third OTP signal= . . . =the N+1^(th) OTPsignal=0. Therefore the final output=the first OTP signal.

Thereafter, when it is desired to modify the output signal or write anew adjusting data for outputting a desired output signal, the values ofthe desired signal and the first adjusting signal are performed XORtogether for obtaining the second adjusting data. The second adjustingdata is then written into the second adjusting OTP element 202 using thewriting device 220. According to aforementioned circuit design rule ofthe present invention, the final output signal=the first OTP signal⊕thesecond OTP signal⊕ . . . ⊕the N+1^(th) OTP signal, wherein the third OTPsignal=the fourth OTP signal= . . . =the N+1^(th) OTP signal=0 exceptfor the first and the second OTP signal. Therefore the final outputsignal=the first OTP signal⊕the second OTP signal.

Accordingly, the modification of the output signal or the writing ofadjusting data into adjusting OTP elements can be implemented byperforming XOR on adjusting data written in the adjusting OTP elementsto generate a desired adjusting signal. Thus, N groups of adjusting OTPelements provides N times programming capability.

The present invention is also directed to a multiple-time programmingmethod using OTP elements. The multiple-time programming method may beimplemented by using the aforementioned apparatus and can be describedas follows.

First, N+1 groups of adjusting OTP element 200˜208 capable of outputtingOTP signals are provided. Next, XOR is performed on the values of theOTP signals from the first group of adjusting OTP element 200 and thesecond group of adjusting OTP element 202 to output a first adjustingsignal. Subsequently, XOR is performed on the values of the firstadjusting signal and the OTP signals from the third group of adjustingOTP element 204 to output a second adjusting signal. Likewise, theprocess of XOR is continued until the values of the N−1^(th) adjustingsignal and the OTP signals from the N+1^(th) group of adjusting OTPelement 208 are performed XOR together to output the final signal.

It is understood from above descriptions, the final output signal=thefirst OTP signal⊕the second OTP signal⊕ . . . ⊕the N+1^(th) OTP signal.

When modification to the IC is desired for the first time, the writingdevice 220 is used to write the first adjusting data into the firstadjusting OTP element 200 only. According to aforementioned circuitdesign rule of the present invention, the final output signal=the firstOTP signal⊕the second OTP signal⊕ . . . ⊕the N+1^(th) OTP signal,wherein the second OTP signal=the third OTP signal= . . . =the N+1^(th)OTP signal=0. Therefore, the final output=the first OTP signal.

Thereafter, when further modification to the IC is desired to output adesired output signal or write a new adjusting data in the adjusting OTPelement for modifying the output signal, XOR is performed on the valuesof the desired signal and the first adjusting signal for obtaining thesecond adjusting data. The second adjusting data is then written intothe second adjusting OTP element 202 using the writing device 220.According to aforementioned circuit design rule of the presentinvention, the final output signal=the first OTP signal⊕the second OTPsignal⊕ . . . ⊕the N+1^(th) OTP signal, wherein the third OTP signal=thefourth OTP signal= . . . =the N+1^(th) OTP signal=0 except for the firstand the second OTP signal. Therefore the final output signal=the firstOTP signal⊕the second OTP signal=desired output signal.

Accordingly, the modification of the output signal or the writing ofadjusting data into adjusting OTP elements can be implemented byperforming XOR on adjusting data written in the adjusting OTP elementsto generate a desired adjusting signal.

Accordingly, N groups of adjusting OTP elements provides N timesprogramming capability. From users' aspect, by the aforementionedapparatus and method thereof for multiple-time programming using OTPelements, different output values is obtained according to differentadjusting data written into each adjusting OTP element. Therefore, itallows rewriting of the adjusting data and serves as an MTP element.Furthermore, the manufacturing process of OTP elements is simpler thanthat of MTP elements, thus allow lower production cost and more choiceof capable foundries.

It will be apparent to those skilled in the art that variousmodifications and variations can be made to the structure of the presentinvention without departing from the scope or spirit of the invention.In view of the foregoing, it is intended that the present inventioncover modifications and variations of this invention provided they fallwithin the scope of the following claims and their equivalents.

1. A multiple-time programming apparatus using one-time programming(OTP) elements, comprising: N+1 groups of adjusting OTP elements,comprising a first group of adjusting OTP elements, a second group ofadjusting OTP elements . . . and a N+1^(th) group of adjusting OTPelements, wherein N is an integer greater than 1, wherein each of theadjusting OTP elements outputs an OTP signal; and N logic devices,comprising a first logic device, a second logic device . . . and aN^(th) logic device, wherein N is an integer greater than 1, whereineach of the logic devices outputs an adjusting signal, wherein theN^(th) logic device is coupled to the N+1^(th) group of adjusting OTPelements and the N−1^(th) logic device, for performing XOR on an OTPsignal outputted from the N+1^(th) group of adjusting OTP elements andan adjusting signal outputted from the N−1^(th) logic device, andoutputting an N^(th) adjusting OTP signal, wherein the first logicdevice is coupled to the first group of adjusting OTP elements and thesecond group of adjusting OTP elements for logic a first OTP signal anda second OTP signal outputted from the first group adjusting OTPelements and second group of adjusting OTP elements respectively andoutputting a first adjusting OTP signal.
 2. The multiple-timeprogramming apparatus using OTP elements as recited in claim 1, furthercomprising a writing device coupled to the N+1 groups of adjusting OTPelements for writing a plurality of ajusting data into N+1 groups ofadjusting OTP elements.
 3. The multiple-time programming apparatus usingOTP elements as recited in claim 1, wherein the N+1 groups of adjustingOTP elements comprise a plurality of poly fuses.
 4. The multiple-timeprogramming apparatus using OTP elements as recited in claim 1, whereinthe N+1 groups of adjusting OTP elements comprise a plurality of metaladjustable with laser.
 5. The multiple-time programming apparatus usingOTP elements as recited in claim 1, wherein The N+1 groups of adjustingOTP elements comprise elements programmable for at least one time. 6.The multiple-time programming apparatus using OTP elements as recited inclaim 1, wherein the N+1 groups of adjusting OTP elements compriseelements selected from a group consisting an EPROM, an EEPROM and aFLASH memory.
 7. The multiple-time programming apparatus using OTPelements as recited in claim 1, wherein the logic devices comprise aplurality of XOR elements or XNOR elements.
 8. A multiple-timeprogranunlng method using OTP elements, comprising: providing N+1 groupsof adjusting OTP elements, comprising a first group of adjusting OTPelements, a second group of adjusting OTP elements . . . and an N+1^(th)group of adjusting OTP elements, wherein N is an integer greater than 1,and wherein each of the adjusting OTP elements outputs an OTP signal;performing a logic operation on the OTP signals outputted from the firstgroup of adjusting OTP elements and the second group of adjusting OTPelements, and outputting a first adjusting signal; and performing thelogic operation on the OTP signal outputted from the N+1^(th) group ofadjusting OTP elements and an N−1^(th) adjusting signal for outputtingan N^(th) adjusting signal, wherein the logic operaflon comprises aplurality of XOR operations or XNOR operations.